# Questions tagged [mathematics]

The abstract study of topics encompassing quantity, structure, space, change, and other properties

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If B (observer height, 40,000-feet) and C (distance from observer to horizon, 245-miles) are known then how do I solve for Z (radius of the horizon)? The angle of B-C is 86.46-degrees so the angle of ...
1 vote
72 views

### What is the step-by-step process to solve Angle = ArcCos(R / R+h)?

I'm attempting to calculate the angle to the horizon from various heights to determine how much of the Earth's curve should actually be observable; however, every example and website I've seen that ...
35 views

### Bounding box intersection when crossing date-line and meridian

First of all, I check for general intersections: public bool CheckOverlap(BoundingBox boundingBox) { if (this.UpperRight.Longitude < boundingBox.LowerLeft.Longitude) return ...
18 views

### Map location of unknown point coordinates with two known coordinates and distances between them [duplicate]

I have a problem where I need to find the coordinates of a point which is the intersecting point of two circles. I found a similar question on stackoverflow. I understood to some extent, but not able ...
• 1
150 views

### Calculate the new x and y coordinate of the extent after rotating the map in MapViewer ArcGIS Online

I need to add a symbol to the lower left corner of the map, so every time I rotate the map, I need to calculate the new coordinate of this symbol (which is the new map extent of the lower left corner)....
42 views

### Adjusting GPS location of an object (sled) pulled at a set distance as it moves 3D

A bit of an odd question. We're pulling a sled behind a truck which carries an instrument. We've had to mount the GPS on the truck and are pulling the instrument back and forth in lines in a field. We ...
• 101
1 vote
231 views

### Create a longer line segment from a shorter one?

I do not believe my math is incorrect. This is seems like it could be a projection issue. I start with the following two coordinates ( lon, lat in degrees ) a: [37.821055535000085, -46.84417083099993] ...
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### Multiply and Divide functions do not have correct output in Google Earth Engine

I am trying to calculate standard deviation (observed - mean)/(mean)*100 but I noticed the part where you ".divide(longTermMean)", the math results results are incorrect. I tested out ...
• 33
730 views

### Calculate distance between location and way segment

For my question I have prepared a JsFiddle demo which works well and is fun to play around with: My question is neither about JavaScript nor OpenStreetMap though. It is about mathematics. When you ...
1 vote
16 views

### Reconstruction of a geometric graph: link only vertices with no vertices in-between [closed]

I'm a mathematician who got lost here looking for the name of a graph construction. Sorry if my question is silly/out-of-topic, but it seemed like a good place to ask. I hope my notations are going to ...
• 111
116 views

### Calculate point line distance for a geolocation with altitude

I'm trying to calculate the coordinates (Latitude, Longitude, Altitude) of a point on a line at the minimum distance with another point. I was able to calculate the distance using the formula here: ...
81 views

### Why does the calculation for y-value (when converting from lat/long to a Mercator x,y) involve the width of the map?

I have been looking into converting latitude and longitude into x and y coordinates. This link (first answer) provides a perfect answer for me, but I am wondering why it works. I have figured out why ...
287 views

### Calculating average Azimuth of route

I would like to get an average azimuth of a route (like slope in linear regression). I tried using linear regression to calculate a slope and convert that slope to degrees (azimuth), but I got the ...
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1 vote
654 views

### Calculate GPS elevation angle (Python)

I have two GPS points (Latitude, Longitude, Altitude) the distance between the two points is a maximum of 50 kilometers. How can I calculate the elevation angle? (I want to implement the whole thing ...
• 11
2k views

I have an image file that I am able to overlay perfectly fine onto my Leaflet map with this code: var initLat = 38.9761; var initLon = -77.4875; var imageUrl = '/weather/nexrad/radar.png'; var ...
1k views

### Projection: Mollweide to Equirectangular

I am trying to reproduce in Python a coordinate transformation of a map from Mollweide coordinates (see Figure A) to Equirectangular coordinates (see Figure B) that I saw done in Mathematica in the ...
• 453
1 vote
325 views

### In Tile coordinates, how to get one zoom-level deeper but span the same area?

For an arbitrary tile region defined by (z1, x1, y1), how can we increase z1 to z1 + 1 but span the exact area defined by (z1, x1, y1)? For example, consider t1=(2,2,1). If we want zoom=3 for the same ...
808 views

### Wring mathematical formula for Sentinel-1 in Google Earth Engine

I am trying to find permittivity using Sentinel-1 using following expression It is inverse of Modified Dubois model for soil moisture. I am new to GEE so I tried to break the expression in to small ...
• 43
1k views

### How to convert EPSG:28992 to EPSG:4326?

I have a list of coordinates which I need to convert to longitude and latitude in the following way: What are the math transformations and formulas used to achieve this?
632 views

### Clockwise sorting segments of a polygons

My polygons are divised into an array of lines features. Each segments have only 2 coordinates. I would like to sort those segments clockwise starting from the top-right (north-east) like in the image ...
• 3,603
368 views

### Considering distance in network analysis (Gephi)

I have created a set of nodes (archaeological sites) and ties (connected via certain geographical distances), exported from QGIS. I now have an edge list with weights (distances). Gephi, however, sees ...
163 views

### Band ratio with Euler's number in Google Earth Engine

I've band ratio with exponential equation and Euler's number band_ratio = (0,0039e)^(2,4952*(B2/B4)) Can anyone write it in Google Earth Engine format? Or just input the Euler's number?
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1 vote
399 views

### Subtracting image value from corresponding month from image collection in Google Earth Engine

I have extracted sea surface temperature(SST) images from Google Earth Engine for a specific time period and region var start = ee.Date(2012-01-01); var end = ee.Date(start).advance(1,'month'); ...
335 views

### An application for measuring river length?

I'm aware of the coastline paradox and its application to rivers in that the measured length of a river depends on the resolution of the measurement. Is there an application that calculates the centre ...
• 31
108 views

### Dividing polygon into tiny polygons of particular size

I would like to divide/cut an irregular polygon into tiny polygons of a particular size(1.6m x 1m) in such a way that most of the irregular polygon area has to be utilized (an OPTIMIZATION MODEL) The ...
1k views

### How to determine left and right side of crossing lines? [closed]

Given two lines of which we know the starting XY points and intersecting point, I need to find which line is left and which line is right. The lines are always crossing and can be turned in any ...
• 850
1 vote
217 views

### Determine if a great circle is on the left or right from a point defined by latitude, longitude and bearing

Given A point coordinate on the map specified by latitude and longitude. Shown as "C" on pictures below. Direction where this point is moving, specified by bearing in degrees (0-359), where ...
• 119
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### How can you completely cover the surface of a raster with circles where the radius of the circle is the raster value at its centroid?

This is more of an algorithmic/math problem, but I was wondering if someone could point me in the right direction. There's the common problem of covering a surface with circles of equal sizes, but ...
• 449
998 views

### Math formula to calculate GPS location for weighted GPS data points

I'm working to improve the location and accuracy of a map / data-point driven application. I have a collection of locations of interest. Each location of interest has a collection of data points that ...
• 161
1 vote
111 views

### Time-Based Multilateration

I'm not entirely certain, but I think this forum is most appropriate for this question. I know the location of three observers. A nearby source, who's location is unknown emits a beam of radiation at ...
1 vote
430 views

### Finding line equation (on Earth) using two GPS coordinates

Assuming I have two GPS coordinates, how can I find the equation of Earth horizontal line that passes between them? I tried searching for a method of finding a line on a sphere that passes through two ...
• 121
875 views

### Converting to geodetic latitude, longitude

I’m writing a program to determine a vector between two points on earth by taking the difference of the ECEF vectors for each point. I’m using this algorithm: https://www.mathworks.com/help/aeroblks/...
1k views

### ECEF coordinates to geodetic coordinates: Where is error in calculation?

I know, there are several questions to this topic, but I am just searching for the error in my own equations. I have no deeper geodetic background, but I am trying to understand these formulas instead ...
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1 vote
668 views

### High resolution x,y dataset for Mollweide projection convert to latitude and longitude coordinates

I have a 2D array that's 144000 x 64000 that has some values that are irrelevant to the question. Let's say the array can be used like an X, Y coordinate system. I somehow need to get the Latitude and ...
• 131
1 vote
229 views

### How to transform camera calibration parameters to other coordinate system?

I have all camera calibration parameters (X0, Y0, focal length, R0, P0, P1, K0, K1, coarse rotation, rotation, translation) and position of the image in WGS84 (XYZ in meters) and other parameters like ...
• 121
97 views

### Seeking documentation about non-iterative UTM to Lat-Long projection formulas

In Hager, John W., James F. Behensky, and Brad W. Drew. "The universal grids: Universal transverse mercator (utm) and universal polar stereographic (ups)." DMA technical manual 8358 (1989). I ...
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818 views

### Calculating Center (GPS Point) and Radius (km) of n GPS points

I'm new to GPS and position mapping but i have a background in programing and some of the math related to it. I've been tasked with writing a small golang program that takes n GPS points (DMS) and ...
• 121
1 vote
70 views

### Converting latitude/longitude into a slab number (or item number) and vice versa?

Purpose: To compress the data transmission for the longitude and the latitude. Initially these datas are in the form DD.MM.mmmm: degrees, minutes, ten thousandths of a minute. Latitude stands under 28 ...
527 views

### Calculate weighted azimuth/bearing of a line

Given the line LINESTRING(-9.086532643219698 -7.939337106873815,-1.396102955719698 -0.9775148048290135,-0.780868580719698 -0.7138718839794582,-0.077743580719698 -0.6699297767574899,0.581436106780302 ...
1 vote
50 views

### How is the Point on surface tool calculated in QGIS [duplicate]

I am interested to know how the Point on surface tool works in QGIS 3. I am choosing to use this rather than the Centroids tool which works of the "center of mass" methodology because this creates a ...
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294 views

### Applying a two step floating catchment with boundary limitations

The literature states that gravity models and the two step floating catchment area (which in itself is a version of the gravity model) method for analysing the accessibility of healthcare services by ...
• 3,230
207 views

### How to run a Epanechnikov (parabolic) decay in QGIS 3.6 field calculator

Does anyone know how you would implement a Epanechnikov (parabolic) decay to a field in QGIS field calculator. I am trying to apply varying distance decay functions in order to assess the best ...
• 3,230
593 views

### calculating HRMS using NMEA sentences including GPGGA , GPGSV, GLGSV, QZGSV,QZGSA, GPGSA?

I have NMEA sentences including GPGGA , GPGSV, GLGSV, QZGSV,QZGSA, GPGSA and GNGSA. my goal is to achieve HRMS accuracy meter. produced android devices for special intent gives GP/GN GST nmea message ...
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1k views

### Procedure of transforming coordinates?

I'm trying to understand the math behind this transformation. I should note that I've been able to perform the transformation using GeoPandas, but I'd like to understand what is going on under the ...
• 133
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### How to compare centrality of points in different shaped and sized polygons

Suppose I have several polygons of varying shape and size, each containing a single point. I want to compare the centrality of each point, and determine which point is more central to its polygon. I'm ...
• 141
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### Calculate angle between nodes or point in line in QGIS

I want to check the digitization of line in correct direction, so for that I need to know the angle of each node in line. Is that possible in QGIS?
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25k views

### How to add meters to EPSG:4326 coordinates? [duplicate]

I've some lat/long in EPSG:4326 coordinate system like Eiffel Tower position : ["lat" : 48.858274,"lon" : 2.2944] For automated tests I would like to get, for every points of my ...
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1 vote
432 views

### GRASS GIS: Getting know about stream power index (SPI) computation by r.watershed function

I need to know exact way how stream power index (SPI) is computed by module r.watershed. On the help page is that SPI is α * tan(β), where: α is cumulative upslope area draining through a point per ...
• 1,783
129 views

### Postgresql - problem updating row with complex calculation

A calculation for the replacement value of a tree exists: Variables: index_price for species; circumference of tree; condition measures: vitality, root_injuries, stem_injuries, crown_injuries (A ...
• 645
1 vote